Convenient syntheses and characterization of fluorophilic perfluorooctyl-propyl amines and ab initio calculations of proton affinities of related model compounds

Article abstract of DOI:10.1016/S0022-1139(00)00398-5

A convenient and effective method for the preparation of perfluorooctyl-propyl amines ([R_f8(CH₂)₃]_nNH_3-n (1-3), n=1,2,3; R_f8(CH₂)₃NHMe (4); [R_f8(CH₂)₃]₂NMe (5); R_f8(CH₂)₃NMe₂ (6); R_f8=F(CF₂)₈) via a step by step alkylation with R_f8(CH₂)₃I is described. The fluorophilicity values of 1-6 were determined by GC and range from 0.79±0.07 (1) to 5.3±0.2 (3). Systematic ab initio calculations of proton affinities of model compounds (7a-j) using Hartree-Fock and density functional theory imply that the inserted trimethylene spacer unit efficiently reduces the electron-withdrawing effect of the perfluorinated segment. All structures were verified by multinuclear one- and two-dimensional NMR experiments involving both homo- (¹⁹F-¹⁹F) and hetero-nuclear (¹H-¹³C, ¹H-¹⁵N, ¹⁹F-¹³C) correlations based on the GMQFCOPS and inverse ¹H and/or ¹⁹F detected GHSQC, GHMQC sequences with broadband adiabatic ¹³C-decoupling.